"2001: A Space Odyssey"
The original, "The Day the Earth Stood Still" (Read the book also)
"Things to Come" (1936)
"Metropolis"

Note to Tom. I assume you class "An Inconvenient Truth" as Sci Fi simply because of the vast amount of hot air eminating from parts of Linwood. You probably haven't noticed any change in the climate. grin

just talked to autie. first, his favorite sci-fi is The 10 Commandments and his computer system is down. the storms at auties were not as bad as they were to the north, east, and southeast. alot of power lines down in those areas. P.S. I never really liked Sci-Fi's.

Several of these have been mentioned, but surprisingly some haven't. My list, in no particular order:

The Quiet Earth
Brazil
Blade Runner
Planet of the Apes
Night of the Living Dead / Day of the Dead (both versions)
28 Days Later
Shaun of the Dead
Grindhouse
Gattaca
The Matrix
Back to the Future
Young Frankenstein
Serenity
Metropolis
Close Encounters of the Third Kind
E.T.

logicsound, who said we need just a top ten? You are clearly a film buff, and there are just too many great films that are worthy of mention that would never make such a short list, such as Bill and Ted's Excellent Adventure, or Omega Man, or even Barbarella.

Given the abundance of breast enhancement surgery and little blue pills, I guess you could say any adult film made in the past decade qualifies as science fiction.

Shotgun, it is like naming your favorite child when you have more than one. There are just too many great sci fi movies to pick just one. I enjoy seeing peoples' lists because it helps jog my memory about other films.

Independence Day
The Day the Earth Stood Still (the original)
Forbidden Planet
Star Wars Episodes 4-6
The Fifth Element
A Boy and His Dog
Stargate SG1
Stargate Atlantis
Star Trek Voyager
Close Encounters
Star Trek: The Voyage Home
The Matrix
20,000 leagues under the Sea
Men in Black
AvP

Yes, yes, Enemy Mine. I liked the word play on the title.
But the film, I think is a classic. I loved Louis Gosset Jr. in this movie. By all means, as St. James says above, go see it. A great love story, IMHO